447debbie

Do any of you have any comments regarding using ethanol free gas vs. gas with 10% ethanol. I think my mpg is better with the ethanol free, but I only ran my first two tanks with the 10% ethanol. It seems the mpg has creeped up steadily and I don't know if that's a result of engine break-in or the fact that the gas is becoming more pure with each ethanol free fill up. Once you put 10% ethanol in your tank, you'd have to completely empty the tank to make it ethanol free, or just keep using ethanol free with each fill and eventually the amount of ethanol left is negligible. I chose the latter. I've gone from 25 mpg on the first two tanks, to a solid 27+ mpg now. All that being said, I don't want to run down to practically empty and put a tank of 10% ethanol in just to check to see if the mpg drops. Maybe someone out there has already done this. I have the 2.0 quattro 2011 Audi A5 Cabrio.

Besides possible better mpg, isn't non-ethanol still better for your car, even though manufacturers have supposedly made the fuel components more robust to ethanol? Any thoughts?

KarlFEvans

Where are you buying non-ethanol gas?

I believe ounce per ounce that ethanol does have less energy than gas. So you should get better mileage with zero ethanol.

447debbie

Check out this site for ethanol free gas locations. http://pure-gas.org/

Fithian

I picked up my S5 in Germany and drove through Belgium and Netherlands, then back to Germany. I did not buy gas in Netherlands, since it is the most expensive in Europe except for Finland. In Belgium it was only possible to buy unleaded with ethanol, in Germany there was a choice. I chose ethanol free and probably got 2-3 mpg more than the ethanol crap. When using ethanol gas the mileage drop approaches the percentage of ethanol in the gas. It is hard to find in the US, but, believe it or not, more stations are offering it. pure-gas.org shows all US stations by state, with octane rating and location. I figured that the cost could be 20¢ per gallon more and we would still benefit from the mileage gain.

ayap

Soon all gas stations will have ethanol .. it sucks.

MonzaA5

In North America, Shell 91 is ethanol free. Shell even makes a point of marketing it as such.

uberwgn

The ethanol isn't our friend, but most fuel sold in the USA contains it

g-force

only 5 in the entire state of california!

ChipB

Ethanol has about 1/3 less energy content per gallon than gasoline, and so at 10% mix your MPG in theory will be 3% worse than with ethanol-free gasoline. Measuring gas mileage to 3% accuracy is difficult to do, and very minor changes in driving conditions will make it impossible. The point is that while 10% ethanol gasoline has worse mileage, it's only on the order of 1 MPG, tops.

As for the concern about having to run through several tankfuls of ethanol-free to sufficiently dilute the ethanol in the gas tank - I don't buy it. If you run the tank down to less than 1/8 and fill it up the concentration of ethanol remaining in the tank would be down to about 1% - not enough to notice no matter how carefully you try to measure MPG. I think what you're experiencing is the placebo effect.

447debbie

I don't think it's a placebo effect. I have nine points of increasing mpg. That's statistically significant. It's either the effect of engine break-in or usage of ethanol free. Since I don't let my car get near empty, it takes me awhile to get up to a high enough concentration of pure gas to consider it ethanol free.

http://www.efcog.org/wg/esh_es/Stati...rol_Charts.pdf
See Section 3.7, bullet point 4. This considers a seven point trend to be statistically significant. I have nine.